https://invisible-island.net/xterm/xtoolkit/
XtDisplayStringConversionWarning - issue a conversion warning message
#include <X11/Intrinsic.h> void XtDisplayStringConversionWarning(Display* display, const char *from_value, const char *to_type);
display Specifies the display connection with which the conversion is associated. from_value Specifies the string that could not be converted. to_type Specifies the target representation type requested.
The XtDisplayStringConversionWarning function issues a warning message using XtAppWarningMsg with name "conversionError", type "string", class "XtToolkitError", and the default message string "Cannot convert "from_value" to type to_type". To issue other types of warning or error messages, the type converter should use XtAppWarningMsg or XtAppErrorMsg.
XtAppWarningMsg(3t) X Toolkit Intrinsics – C Language Interface Xlib - C Language X Interface X Version 11 libXt 1.1.XtDisplayStringConversionWarning(3)